In a semiconductor device manufacturing process, various kinds of processing are performed, such as formation of thin films on workpieces, e.g., semiconductor wafers. The semiconductor wafers are conveyed in the course of such processing. Due to the slight contact or sliding contact between individual members during the conveyance, static electricity is prone to being generated in the semiconductor wafers or a wafer boat holding the semiconductor wafers. If static electricity is generated in the semiconductor wafers and thus electrically charging the semiconductor wafers, particles such as dust and the like are likely to adhere onto the semiconductor wafers. This poses a problem in that the yield rate of products gets lowered.
In view of this, it is under study that an electricity removal device for removing static electricity generated in semiconductor wafers is installed in a processing apparatus. For example, JP2005-72559A discloses a substrate processing apparatus including a substrate holding unit for holding a substrate and an electricity removal unit for removing electricity from an atmosphere accommodating the substrate holding unit.
However, in the case that a multiple number of semiconductor wafers to be subjected to such electricity removal exists in a processing apparatus, such as a batch-type vertical processing apparatus, requiring the electricity removal over a wide area, difficulties may occur in uniformly removing static electricity. Thus, demand exists for a device capable of uniformly removing static electricity over a wide area.